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PubMed1991

Heterogeneity of muscarinic receptor subtypes in cerebral blood vessels.

The identity and distribution of muscarinic cholinergic receptor subtypes and associated signal transduction mechanisms was characterized for the cerebral circulation using correlated functional and biochemical investigations. Subtypes were distinguished by the relative affinities of a panel of muscarinic antagonists, pirenzepine, AF-DX 116 [11-2-[[2-[diethylaminomethyl]- 1-piperidinyl]acetyl]-5,11-dihydro-6H- pyrido[2,3-b][1,4]benzodiazepine-6-one], hexahydrosiladifenidol, methoctramine, 4-diphenylacetoxy-N-methylpiperidine methobromide, dicyclomine, para-fluoro-hexahydrosiladifenidol and atropine. Muscarinic receptors characterized by inhibition of [3H]quinuclidinylbenzilate binding in membranes of bovine pial arteries were of the M2 subtype. In contrast pharmacological analysis of [3H]-quinuclidinylbenzilate binding in bovine intracerebral microvessels suggests the presence of an M4 subtype. Receptors mediating endothelium-dependent vasodilation in rabbit pial arteries were of the M3 subtype, whereas muscarinic receptors stimulating endothelium-independent phosphoinositide hydrolysis in bovine pial arteries were of the M1 subtype. These findings suggest that characteristics of muscarinic receptors in cerebral blood vessels vary depending on the type of vessel, cellular location and function mediated.

Animals↗
PubMed1991

Reduction of cardiac outward currents by alpha-1 adrenoceptor stimulation: a subtype-specific effect?

In rat ventricular myocytes, the effects of alpha adrenoceptor stimulation on outward currents were studied by means of the whole cell voltage-clamp technique. Phenylephrine (30 microM) in the presence of propranolol (1 microM) to block beta adrenoceptors reduced voltage-activated transient outward current. Both components of transient outward current were affected, i.e., peak current (Ipeak) was reduced by 25.3 +/- 1.8%, the outward current at the end of a clamp step (Ilate) was reduced by 39.1 +/- 3.5% (n = 5; holding potential -40 mV, clamp step to +20 mV). In order to describe the alpha-1 adrenoceptor subtypes involved in this action, the effect of phenylephrine was also investigated after pretreatment of the cells with various antagonists. Pretreatment with prazosin (0.3 microM) abolished completely the phenylephrine effect. The alpha-1A adrenoceptor subtype-selective antagonists 5-methylurapidil and (+)-niguldipine (0.1 microM each) and the irreversible alpha-1B adrenoceptor subtype antagonist chloroethyl-clonidine (100 microM) blocked the phenylephrine effect on Ipeak, but merely attenuated the effect on Ilate, whereas pretreatment with a combination of chloroethylclonidine and (+)-niguldipine suppressed the phenylephrine-induced effect on both outward current components just like prazosin did. In conclusion, stimulation of both adrenoceptor subtypes is required for reduction of Ipeak, but stimulation of either alpha-1A or alpha-1B subtype is sufficient for reduction of Ilate. Therefore, stimulation of both alpha-1 adrenoceptor subtypes contributes to the phenylephrine-induced reduction in transient outward currents of isolated rat myocytes.

Adrenergic alpha-Antagonists↗
PubMedDate not supplied

Receptor subtype-specific dopaminergic agents and unconditioned behavior.

When all of the data concerning the role of D1 and D2 receptors in the control of unconditioned behaviors are taken together a fairly consistent picture begins to emerge. Considering first the normosensitive animals, it appears that D1 and D2 receptors are interdependent in their involvement in the control of locomotor activity. Stimulation of either receptor subtype leads to increases in activity although D2 agonists generally have a larger effect on activity than D1 agonists. Subeffective doses of D1 and D2 agonists (or D1 and D2 antagonists) have a synergistic action when co-administered. Injections of antagonists specific for either receptor subtype leads to a decrease in unstimulated locomotor activity or a diminution in the effects of agonists stimulating either receptor subtype. Besides locomotor activity, stimulation of D2 receptors produces yawning but a consistent effect on grooming has not been seen; D2 receptor stimulation also produces stereotyped behaviors. Again, there seems to be an interdependence between the two receptor subtypes; yawning or stereotypy produced by D2 receptor stimulation is blocked by either D2 or D1 antagonists. Stimulation of D1 receptors produces grooming and small perioral movements but not stereotyped behaviors like those typically seen following large doses of D2 agonists or DA agonists not specific a receptor subtype. Unlike D1 receptor-stimulated locomotor activity which is antagonized by D2 receptor blockers, grooming and perioral movements are not (but see Ref. 81). Thus, D1 receptor-mediated grooming and perioral movements seem to be exceptions to the otherwise general finding that co-stimulation of the two receptor subtypes needed for the expression of D1 or D2 agonist effects in normosensitive rats and mice. The apparent need to stimulate both D1 and D2 receptors to produce locomotor and some other unconditioned behaviors in normosensitive animals is lost in chronically denervated animals that are supersensitive to the effects of DA or DA agonists. However, there appear to be important species differences. Generally, in rodents undergoing unilateral or bilateral 6-OHDA-induced destruction of the nigrostriatal DA system, the locomotor effects of D1 agonists are not blocked by D2 antagonists and those of D2 agonists are not blocked by D1 antagonists. Similar results have been reported following chronic treatments with catecholamine depleting drugs. Thus, stimulation of either D1 or D2 receptors alone in DA supersensitive rodents appears to be sufficient to produce locomotor activity. In primates made DA supersensitive either with MPTP or as a result of Parkinson's disease, on the other hand, D2 but not D1 agonists are effective in reversing locomotor deficits.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

M3-muscarinic receptor subtype predominates in the bovine iris sphincter smooth muscle and ciliary processes.

The distribution of mRNAs encoding muscarinic acetylcholine receptor (mAChR) subtypes (M1, M2, M3, and M4) was investigated in the bovine iris-ciliary body by Northern blot hybridization with subtype-specific oligonucleotide probes that were complementary to unique regions of the M1, M2, M3, and M4 mAChRs. Whole rat brain RNA, which contains all four subtypes, was employed as a positive control. Both the iris sphincter and the ciliary processes were found to contain predominantly the M3 mAChR subtype and minor amounts of the M2 subtype. Traces of the M4 subtype were detected also in the ciliary processes.

Animals↗
PubMed1990

Structure and diversity of HLA-B27-specific T cell epitopes. Analysis with site-directed mutants mimicking HLA-B27 subtype polymorphism.

HLA-B27 subtype polymorphism is amenable to differential recognition by CTL. Site-directed mutagenesis was used to construct a series of HLA-B27 mutants reproducing most of the changes occurring in the natural subtypes. The reactivity of 21 anti-HLA-B27 CTL clones was examined with these mutants to address three issues concerning the alloreactive response against HLA-B27: 1) diversity of clonotypic specificities, 2) structural features of the epitopes recognized by these clones, and 3) role of individual positions in the differential recognition of HLA-B27 subtypes. Virtually all CTL clones displayed unique reaction patterns with the mutants, indicating a corresponding diversity of epitopes. However, these share some molecular features, such as certain amino acid residues and related locations. Individual mutations induced complex effects on multiple B27-specific CTL epitopes, revealing some of their very precise stereochemical constrains. An important feature of HLA-B27 subtype polymorphism is that every individual change was relevant, altering recognition by many CTL clones. Although the specific set affected by each mutation was partially different, the global number of clones affected by most changes was very similar. This suggests that the antigenic profile of any given subtype is not dominated by one particular change but is uniquely defined by its corresponding set of changes. An exception was the change at position 152, which totally abrogated recognition by all 20 anti-B*2705 CTL clones. This effect decisively influences the profound differences in T cell recognition between B*2705 and the two subtypes, B*2704 and B*2706, carrying this change. The results are compatible with the idea that HLA-B27 allorecognition may involve multiple peptides bound to the alloantigen on the cell surface.

Amino Acid Sequence↗
PubMed2006

Functional characterization of histamine receptor subtypes in a human bronchial epithelial cell line.

Histamine is a well-known mediator eliciting a broad range of responses in different cell types. Four different subtypes of G protein-coupled histamine receptors (H1-H4) have been cloned and pharmacologically characterized. However, involvement of the different histamine receptor subtypes in immunomodulatory functions of bronchial epithelium has only been investigated marginally. The expression and function of histamine receptor subtypes on the human bronchial epithelial cell line BEAS-2B was analyzed by PCR, intracellular Ca++ -measurements and ELISA. We show mRNA expression of the histamine receptor subtypes H1, H2, and H3, but not H4 in the human bronchial epithelial cell line BEAS-2B. Using intracellular Ca++ -measurements, we demonstrated functional expression of the H1 and H3 receptors. To characterize the biological properties of histamine in airway epithelial biology, we also investigated its effects on cytokine secretion by BEAS-2B cells. Thereby, we were able to show up-regulation of the proinflammatory mediators IL-6 and CXCL8/ IL-8 via activation of the H1, H2 and H3 receptor subtypes. The Th1 cytokines CXCL9/MIG and CXCL10/IP-10 and the chemokine CCL5/RANTES were regulated in a distinct manner: Whereas histamine inhibited the IFN-gamma/TNF-alpha-induced secretion of MIG via the histamine receptor subtypes H1, H2, and H3, the histamine-induced suppression of RANTES was due to activation of the H2 and H3 receptors, while reduction of cytokine-triggered IP-10 secretion was mediated only by triggering the H2 receptor. In summary our data provide evidence that histamine released during allergic lung diseases exerts regulatory influence on airway epithelial cells.

Bronchi↗
PubMed1991

Immunological detection of muscarinic receptor subtype proteins (m1-m5) in rabbit peripheral tissues.

Employing subtype-specific antisera, we have measured the relative levels of five muscarinic receptor subtype proteins (m1-m5) in rabbit peripheral tissues. Immunoprecipitation assays demonstrated the presence of four distinct receptor proteins (m1-m4), which showed notable differences in their tissue distribution. Significant amounts of m5 receptors were not detected in any of the tissues examined. High levels of m1 receptors were found in sympathetic ganglia and submaxillary gland. The m1 receptor was the predominant subtype in vas deferens. Muscarinic receptors of the m2 type were present in varying proportions in all tissues examined, being the major subtype in sympathetic ganglia, ileum, and uterus and the only subtype detected in rabbit atrium. The m3 receptor protein was abundant in submaxillary gland but was not detected at appreciable levels in other tissues studied. Receptors of the m4 type represented a major subtype in peripheral lung and were also present, although at lower levels, in uterine and ileal tissues.

Animals↗
PubMedDate not supplied

Fine needle aspiration cytodiagnosis of Hodgkin's disease and its subtypes. I. Scope and limitations.

The fine needle aspiration (FNA) smears and paraffin-embedded sections from 89 cases with a cytologic and histologic diagnosis of Hodgkin's disease (HD) and 27 cases with minor or major cytohistologic discrepancies were reviewed. The accuracy of the initial cytologic study was found to be 91.8% for diagnosing HD and 58.1% for classifying its subtypes. Following review, 87 of the 89 agreement cases remained classified as HD. Of the 27 cases with initial cytohistologic discrepancies, 12 were classified as HD and 10 were categorized as lymphocytic or non-Hodgkin's lymphoma by both cytology and histology upon review. Following review, the accuracy of FNA cytology for the diagnosis of HD improved to 98.0%, with 71.4% correct subtyping. The greatest limitation of cytologic subtyping was in cases of nodular sclerotic HD: only 3 of 17 cases could be subtyped even after review. The cytomorphologic features of the HD subtypes are described, and the difficulties encountered in the cytodiagnosis of HD are discussed at length. The results of this study indicate that FNA cytology is a useful tool not only for the diagnosis of HD, but also for its subtyping.

Adult↗
PubMed1988

HA2 subunit of influenza A H1 and H2 subtype viruses induces a protective cross-reactive cytotoxic T lymphocyte response.

Influenza H1 subtype-specific CTL can be induced by secondary stimulation of a hybrid protein of the first 81 amino acids of the viral NS1 non-structural protein and the HA2 subunit of A/Puerto Rico/8/34(H1N1) hemagglutinin. In addition, a derivative of this protein with 65 amino acids deleted from the N-terminal end of HA2 can also generate H1 subtype-specific CTL in bulk cultures. CTL clones established by stimulation with the derivative protein demonstrated cross-reactive lysis of target cells infected with virus strains of the H1 and H2 subtypes. Cold target competition experiments with CTL clones as effectors demonstrated that the Ag specificity between these two hybrid proteins is identical. Adoptive transfer of the CTL clone significantly reduced virus titers in the lungs of mice infected with the virus strains of the H1 or H2 subtype but not those infected with the H3 subtype virus in vivo, which reflects the in vitro CTL clone activity. These experiments demonstrate that an epitope on the hemagglutinin that is conserved on virus strains of the H1 and H2 subtypes induces a protective CTL response. These results suggest an alternative approach for developing influenza vaccines by using conserved antigenic sites on the hemagglutinin HA2 subunit to avoid the problem of frequent antigenic mutations of the HA1 subunit antibody binding sites.

Animals↗
PubMed1985

Recognition of influenza virus hemagglutinin by subtype-specific and cross-reactive proliferative T cells: contribution of HA1 and HA2 polypeptide chains.

The recognition of influenza virus hemagglutinin (HA) by T lymphocytes was examined by assaying the T cell proliferative response of influenza virus-primed T cells to purified HA of different influenza A subtypes or to isolated heavy (HA1) or light (HA2) polypeptide chains of the HA molecule. The proliferative response to HA was dependent on the activation of an Ly-1+2- subset of T cells and required the presence of nylon wool-adherent, radiation-resistant accessory cells. T cells from mice primed by infection with one strain of type A influenza virus cross-reacted with other purified HA not only of the same subtype as the priming virus but also of serologically distinct subtypes of influenza A (but not B) virus. The response of virus-primed T cells to the homologous HA or to HA of the same subtype was shown to involve recognition of determinants on both the HA1 and the HA2 chains. The recognition of HA of different subtype by cross-reactive T cells appeared to be directed predominantly to determinants on HA2. Because the antibody response to influenza virus HA is not cross-reactive between subtypes and is directed predominantly to determinants on HA1, the present results indicate that at least some of the determinants on HA recognized by T cells are different from those recognized by B cells and that the HA2 chain may be involved primarily in stimulation of T cell rather than B cell immunity.

Animals↗
PubMed1977

Subtyping of hepatitis B surface antigen and antibody by radioimmunoassay.

The hepatitis B surface antigen (HBSAg) has been shown to possess distinct subtypes adw, ayw, adr, and ayr). A commercially available solid phase radioimmunoassay for antibody to HBSAg (Ausab, Abbott Laboratories North Chicago, Ill.) has been modified to detect the subtypes of HBSAg as well as the subtype-specific anti-HBS reactivities to detect the subtypes of HBSAg as well as the subtype-specific anti-HBS reactivities (anti-d, anti-y, and anti-w). This method has the advantages of general availability, ease of performance, and increased sensitivity over conventional subtyping methods of agar gel diffusion and counterelectrophoresis.

Agar↗
PubMed1983

[Synergistic receptor subtypes: an explanation for reserve receptors and for different intrinsic activities of full and partial agonists. Studies on the effect of substance P and its analogs on guinea pig ileum].

The contractile response of guinea-pig ileum to substance P consists of an initial rapid phasic contraction followed by a lower tonic contraction. Both contraction phases can be changed independently of each other. Substance P analogues differ in their ability to induce the phasic and tonic contraction. The structure-activity profile (calculated from ED50) for C-terminal substance P fragments and acylated analogues differ from the structure-affinity profile (calculated from the dissociation constant which was estimated by the desensitization method). These results suggest the possible existence of two substance P receptor subtypes that have different affinities for substance P analogues. Both are coupled with an increase in cytoplasmatic Ca++ and with contraction. Stimulation of SPCa-i (SPCa-influx) receptors seems to open calcium channels in the smooth muscle membrane while SPCa-r (SPCa-release) receptor stimulation seems to release membraneous Ca++. Such synergistic subreceptors could be the cause of the pharmacological phenomenon of spare receptors. If this is the case, then the intrinsic activity would reflect differences in the affinity or the selectivity of analogues for these subreceptors. Partial agonists activate only one synergistic receptor subtype or activate synergistic as well as antagonistic subtypes with similar affinities. Mixed agonist-antagonists are agonists of one, and antagonists of the other synergistic receptor subtype. Organ-selective stimulatory effects of certain analogues can be explained by the various subtypes being distributed in a different fashion between different organs. The possibility to detect the presence of different receptor subtypes from the shift of dose response curves by irreversible antagonists and from the shift of binding curves by GTP and ions is discussed.

Acetylcholine↗
PubMed1982

Characterization of alpha-adrenergic receptor subtypes in the rat renal cortex. Differential regulation of alpha 1- and alpha 2-adrenergic receptors by guanyl nucleotides and Na.

We have used the subtype-selective radioligands [3H]prazosin (an alpha 1-adrenergic antagonist) and [3H]yohimbine (an alpha 2-adrenergic antagonist) to examine alpha-adrenergic receptors in rat renal cortical membranes. Under the conditions used in this study, [3H]prazosin bound only to alpha 1-adrenergic receptors, whereas [3H]yohimbine bound only to alpha 2-adrenergic receptors; the two radioligands were completely selective and did not bind to a common site. The ratio of alpha 2- to alpha 1-adrenergic receptors was about 3:1. Guanyl nucleotides decreased the affinity of epinephrine at both receptor subtypes, but this effect was greater at the alpha 2-receptor and, according to computer analysis, occurred through different mechanisms at the two receptor subtypes. NaCl decreased the affinity of epinephrine at both alpha-receptor subtypes; this effect was more Na+-selective at alpha 2- than at alpha 1-receptors. Guanyl nucleotides and NaCl were additive in decreasing the affinity of epinephrine at the alpha 1-receptor but were synergistic at the alpha 2-receptor. In addition, NaCl increased specific binding of [3H] yohimbine but had no effect on the binding of [3H]prazosin. This enhancement of [3H] yohimbine binding was Na+-specific and fully reversible, and represented an increase in maximal binding capacity. Although binding of epinephrine to both alpha 1- and alpha 2-receptors could be modulated by guanyl nucleotides, we were unable to detect inhibition by epinephrine of basal or hormone-stimulated adenylate cyclase activity. Thus, separate alpha 1- and alpha 2-adrenergic receptors can be detected in the rat renal cortex and binding to both receptor subtypes can be regulated by guanyl nucleotides and Na+ X Na+ may directly interact with alpha 2- but not alpha 1-adrenergic receptors in the renal cortex. Our findings with renal cortical membranes indicate that regulation of agonist binding at alpha-adrenergic receptor subtypes by guanyl nucleotides and Na+ is not limited to alpha 2-adrenergic receptors, as previously reported with other tissues.

Adenylyl Cyclases↗
PubMed1983

Monoclonal antibodies to HBsAg: a study of their specificities for eight different HBsAg subtypes.

Spleens from high responder Biozzi mice immunized with purified HBsAg of adw2, adw4 and ayw3 subtypes respectively were fused with N5-1 mouse myeloma cells. Over 30 clones with anti-alpha activity were obtained (principally from fusion adw2) as well as numerous clones with restrictive anti-HBs reactivity. The aim of this study was to characterize 9 different monoclonal antibodies with restrictive reactivity in comparison to a monoclonal anti-alpha antibody. Two different techniques were used: immunodiffusion and enzymoimmunoassay. Already known specificities or common reactivity between some subtypes were found, as w4, subdivision of ayw3 subtype, antigenic determinant common to w4 and adr, absence of the same determinant in adw2 and ayw1, the 2 subtypes having the highest capacity to absorb anti-alpha. Other monoclonal antibodies indicated the presence of previously unidentified subtype specificities: one of them recognized all HBsAg with d determinant but also ayw4, another recognized all HBsAg with y determinant but also adr, 2 others recognized determinants present completely or partially (spur formation) in many subtypes, another one recognized ayw4 and adw4 but also adw2. The combination of new tools such as monoclonal antibodies and synthetic peptides should facilitate the analysis of HBsAg.

Animals↗
PubMed1982

RDC depressive subtypes: are they valid?

Ninety patients meeting the Research Diagnostic Criteria (RDC) for major depressive disorder were further diagnosed using the RDC depressive subtypes. Patients with specific RDC subtype diagnoses were compared to those who did not meet the subtype criteria on several variables, including family history, illness course, work history, social history, previous treatment, quality of remissions, and symptomatology. Several items significantly differentiated patients diagnosed as primary, psychotic, and situational from those not so diagnosed: this supports the validity of these subtype categories. However, the study did not support the validity of the incapacitated, agitated, and retarded subtypes. No conclusions could be drawn regarding the endogenous, simple, or recurrent unipolar depressive subtypes.

Adult↗
PubMed1995

[5-hydroxytryptamine (serotonin) receptors--nomenclature and classification of types and subtypes].

5-HT receptors represent a superfamily of receptors with the largest known number of receptor subtypes. At present 15 receptor subtypes of three groups has been recognized. The 5-HT1 subfamily of receptors contains subtypes 5-HT1A, 5-HT1B, 5-HT1D, 5-HT1E, and 5-HT1F; activation of all of them results in the inhibition of adenylylcyclase. The subfamily of 5-HT2 contains subtypes 5-HT2A, 5-HT2B, and 5-HT2C; their activation leads to the stimulation of PLC. Finally, subfamily of miscellaneous 5-HT receptors contains subtypes 5-HT3, 5-HT4, 5-HT5, 5-HT6, and 5-HT7; some of them has been cloned, however, our knowledge on their function is still minimal. 5-HT receptors participate in many physiological functions and a disturbance in serotonergic neurotransmission might cause several types of disease. 5-HT plays an important role in depression; to cure this disease, drugs which increase levels of this neurotransmitter are used. A new drug group called Selective Serotonin Reuptake Inhibitors (SSRI) has been recently discovered. These drugs block the reuptake of 5-HT into nerve endings. There is an intensive search for new selective agonists as well as antagonists which could be use not only in the classification of receptor subtypes but which also possess certain therapeutic potential.

Animals↗
PubMed1995

Occurrence of respiratory syncytial virus subtypes in Mexican infants with acute lower respiratory tract disease.

The occurrence of respiratory syncytial virus (RSV) subtypes in Mexico City was studied by searching for the virus in nasopharyngeal aspirates of 82 infants, less than 12 months of age, hospitalized for acute lower respiratory tract disease with diagnosis of bronchitis, bronchiolitis, pneumonia and laryngotracheobronchitis. The presence of respiratory virus was determined by observation of cytopathic effect in cell monolayers; samples which produced a clear syncytia were considered positive and were treated with anti-respiratory syncytial virus serum. Viral infectivity was neutralized in 21 samples which were regarded as having RSV. These specimens were characterized into subtypes A and B with specific monoclonals by indirect immunofluorescence. Subtype A predominated over subtype B, 19 vs. 2. Patients with pneumonia and laryngotracheobronchitis had subtype A and both subtypes were found in infants with bronchitis and bronchiolitis.

Acute Disease↗
PubMed1993

Application of transfected cell lines in studies of functional receptor subtype selectivity of muscarinic agonists.

Chinese hamster ovary cell lines which stably express individual subtypes of muscarinic acetylcholine receptors (m1-m5) were used to assess the potential selectivity of known muscarinic agonists in effecting coupling of different receptor subtypes to signal transduction mechanisms. Phosphoinositide hydrolysis was measured in m1-, m3- and m5-Chinese hamster ovary cells, whereas inhibition of forskolin-mediated cyclic AMP formation was measured upon the activation of m2 and m4 muscarinic receptors. The two muscarinic agonists pilocarpine and McN-A-343 were notably subtype selective on a functional basis. Pilocarpine was more efficacious in stimulating Phosphoinositide hydrolysis linked to m1 as compared to either m3 or m5 muscarinic receptors. On the other hand, McN-A-343 produced marked inhibition of cyclic AMP formation in m4-Chinese hamster ovary cells but only a small response at m2 receptors. The subtype selectivity of pilocarpine and McN-A-343 in these cases was not due to differences in the level of expression of muscarinic receptors in the various cell lines. In contrast, equalizing receptor number in pairs of cell lines masked apparent selectivities in other cases. Our data highlight the functional discrimination of pilocarpine and McN-A-343 among muscarinic receptor subtypes and emphasize the importance of using cell lines which express an equal number of receptors in the process of searching for subtype selective agonists.

(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethy↗